11 Different Types of Lasers
The laser technology sector has seen an explosion in methods and profound increases in power and improvements in beam quality since the first lasers were created five decades ago. The important types of the wide variety of technologies developed to create coherent, collimated light beams are summarized below. Each of these classifications has spawned variants, some of which may become key technologies in their own right.
Listed below are 11 different types of lasers:
Fiber lasers are a category of solid-state lasers that integrate an optical fiber as the lasing medium. They are known for high power, power efficiency, and remarkable beam quality. The lasing process takes place in the fiber medium, typically rare-earth-doped with erbium or ytterbium. Fiber lasers deliver high power and power efficiency, operating from low watts to high kilowatts. They create exceptionally efficient output energy from electrical power. This efficiency is achieved due to the distributed (i.e., not concentrated) gain medium (the fiber) and the resulting ability to lose heat. They create excellent beam quality, with narrow beam divergence and a near-perfect Gaussian beam profile. This allows precise focusing, suiting applications requiring high precision and small area energy application. They’re compact and flexible in design. The fiber's flexibility allows for easy delivery of the radiation, suiting integrated applications and complex/flexible delivery paths.
Fiber lasers are stable and robust. A solid-state lasing medium and the absence of moving parts render them unaffected by the environment to a high degree and low maintenance. They enable wide wavelength selection, from infrared (IR) to ultraviolet (UV). The choice of the dopant defines the operating wavelength. Fiber lasers are applicable to most sectors: manufacturing, telecommunications, defense, medical, research, and spectroscopy.
Gas lasers use a gas mixture as the active lasing medium. The lasing is typically initiated by an electrical arc, which triggers stimulated emission. Variations within the class are significant in their different capabilities in wavelength and power, though their structures and operation are similar. Helium-neon (HeNe) lasers employ a mixture of helium and neon as the active medium. They produce (visible) red light at 632.8 nanometers (nm) and are suited to low-power, eye-visible applications. Carbon dioxide (CO2) lasers use a mixture of carbon dioxide, nitrogen, and helium as the active medium. They generate infrared (IR) light at a wavelength of 10.6 micrometers (μm). High power at low construction cost makes them widely used in industry for cutting, etc. Argon-ion lasers use ionized argon as the active medium. They emit visible light at various wavelengths. They are used in display systems and in research.
Excimer lasers use a blend of noble gases as an active medium: argon, krypton, and xenon, with fluorine or chlorine. They produce ultraviolet (UV) light at selected wavelengths, defined by the gas mixture. They are widely used in medical and industrial applications. Krypton-ion lasers use ionized krypton as the active medium. They emit visible light in the red and green spectra. These lasers are used in scientific research and display technologies. Nitrogen lasers use nitrogen (N2) as the active medium. They produce pulsed UV and are used in research, spectroscopy, and laser fluorescence.
Excimer lasers are an example of a subcategory morphed into a standalone classification. They are a type of gas laser, but their properties differ in key regards from general gas lasers, and they have characteristics that make them optimal for a number of applications. They can deliver ultraviolet (UV) emission at a relatively low cost, which is an unusual and useful feature. Some examples of excimer lasers are those available with 193 nm emissions (argon fluoride, ArF), 248 nm (krypton fluoride, KrF), and 308 nm (xenon chloride, XeCl).
Excimer lasers only operate in pulsed mode, with high peak power and short duration. This makes them suitable for precise material ablation and micro-material processing applications. They are known for their strong photoablation effects, as the high-energy UV photons break chemical bonds in target materials, removing atoms in a controlled and precise manner. This property makes excimer lasers particularly valuable in semiconductor fabrication (microlithography), LASIK eye surgery, and dermatology.
Semiconductor lasers or diode lasers use a p-n junction arrangement as the active medium. They are compact in size, have high efficiency, and are versatile. Semiconductor lasers are structurally simple, as they are directly electrically pumped (i.e., not laser, arc, or flash-tube-initiated). Applying a forward bias current to the junction triggers the emission of laser light, as holes and electrons meet at the junction and are canceled out, with the emission of a coherent photon. Diode lasers are extremely compact, often measuring only a few millimeters, which allows for easy integration into devices and laser arrays. This is particularly useful for fiber-optic comms applications and for portable devices. They have high electrical efficiency, using only slightly more electrical power than they emit as laser radiation, making them suitable for battery-powered devices. Their class output across various types covers various wavelengths, defined by semiconductor dopants, bandgap, and amplifier structure: infrared, visible, and ultraviolet. This equips the class for most applications. These lasers are also used as efficient pump sources for other types of lasers, such as Nd:YAG, providing a compact alternative to xenon flash-tube pumping.
Dye lasers are a class that uses organic dye solutions as the active medium. They offer great tunability across the visible and near-infrared spectrum. Dye lasers can generate high-energy pulses of short duration. A typical xenon discharge tube exciting a dye laser will deliver intense bursts of light. This is ideal for time-resolved spectroscopy, photochemistry, and laser-induced breakdown spectroscopy. They are highly wavelength tunable across a broad spectral range, by changing the dye solution or adjusting the optical amplification cavity. This results in a wide range of wavelength radiation, from UV to NIR (near-infrared). Dye molecules result in a wide gain bandwidth, generating ultrashort pulses of femtosecond or picosecond durations. This makes them suited to research and medical applications, allowing very precise control of energy levels.
Solid-state lasers use a solid, generally doped crystalline material as the active medium. They have advantages and are heavily used in several fields. Solid-state lasers are capable of producing high-power output, in continuous wave (CW) or pulsed mode at high efficiency. They cover a wide range of emission wavelengths (IR to visible UV) depending on the dopants. Examples are: neodymium-doped yttrium aluminum garnet (Nd:YAG) lasers, erbium-doped fiber lasers, and titanium-sapphire lasers. They typically produce beams with excellent spatial and temporal coherence, enabling close focus, limited divergence, and low beam distortion.
Solid-state lasers are renowned for stability and reliability, as the solid-state medium is robust and less susceptible to environment, vibrations, and misalignments. Q-Switching (rapid modulation) and mode-locking (rapid, ultrashort bursts) enable them to produce short-duration, high-intensity laser pulses. This is useful in applications such as laser marking, lidar systems, laser ranging, and ultrafast spectroscopy. Many solid-state lasers can be directly pumped using laser diodes, enabling simplified designs, and improved power efficiency.
Chemical lasers generate laser light from a chemical reaction excitation source. Violent exothermic chemical reactions between two or more initial chemicals produce a population inversion (of electrons in the excited state) resulting in stimulated emission for very high outputs. High output is possible, often in the megawatt range, from compact sources. This intensity makes chemical lasers valuable for military systems, laser-induced plasma, and high-energy physics. They can be operated in CW or pulsed mode. Pulse-mode chemical lasers are often used in military and defense applications, including directed-energy weapons and laser-based missile defense systems.
The chemical oxygen-iodine laser (COIL) is a specific type used primarily in research and development. It operates by reacting chlorine gas and hydrogen peroxide to produce energetic oxygen and iodine molecules, which undergo stimulated emission. COIL lasers have been studied for potential applications in cutting and welding, materials processing, and space propulsion systems. This class of laser was popular in military development in the 1970s, but they’ve largely been supplanted by technically more complex but less violent and more easily contained devices. Chemical lasers have severe limitations, including the requirement for violent chemical reactants, structure complexity, and the need for specialized handling and safety measures of the reactive agents involved.
Metal-vapor lasers excite metal vapor as the active medium to generate laser light. They operate by exciting metal atoms or ions to higher energy levels, which then undergo stimulated emission to produce coherent laser radiation. Metal-vapor lasers have uniquely useful properties, such as the ability to emit in the extreme UV spectrum. These lasers use a vaporized metal as the active medium. Common metals used include: copper, gold, silver, and mercury. The metal vapor is typically created by heating a metal sample to its vaporization temperature, using another laser type. They primarily emit in the visible and UV spectra, depending on the metal used. Copper-vapor lasers emit green light at around 510 nm, while gold-vapor lasers emit yellow light at around 628 nm.
Metal vapor lasers are capable of producing high energy emissions, delivering intense radiation with high overall efficiency. They are ideal for applications that require high-energy output. These devices can generate short pulses in the nanosecond range. This property is particularly useful in applications that require precise temporal control, such as laser-induced breakdown spectroscopy and time-resolved spectroscopy. They have been used in various industrial and scientific applications. Copper-vapor lasers, for example, are employed in laser marking, laser engraving, holography, and scientific research. Gold-vapor lasers have been utilized in medical treatments, dermatology, and photochemical processes. The extreme UV lasers used in the highest resolution lithography processes are metal-vapor based, using tin vapor to produce laser light at near X-ray frequencies. This short-wavelength light has allowed higher-resolution imaging to reduce microprocessor feature sizes to allow a higher density of components on a single wafer.
Metal-vapor lasers can produce laser beams with high beam quality, characterized by a well-defined focus, low divergence, and good spatial coherence. They are excited using various methods: electrical discharge, laser excitation, and electron-beam excitation, among others.
FELs use the influence of a magnetic field on a beam of high-energy electrons to trigger stimulated emission. The free electrons originate from a linear accelerator, and their energy level determines the wavelength of the resultant radiation. FELs can cover a broad range of wavelengths, from the infrared to the X-ray region, because of the precise control of electron energy levels. This wide tunability makes FELs versatile for a wide range of applications. Through self-amplified spontaneous emission (SASE), they amplify the radiation. The effect on the electron beam of an oscillating magnetic field causes the electrons to emit radiation. This stimulates further emission, leading to amplification.
FELs can produce remarkably high peak powers and femtosecond pulses. This makes them suited to studying nonlinear phenomena, high-intensity interactions, and investigations of ultrafast dynamics. The intense and tunable X-ray beams emitted are ideal for image technologies such as: X-ray diffraction, X-ray microscopy, and X-ray spectroscopy in various fields of fundamental research. A sub-category is free electron laser oscillators (FELOs). These use resonant optical cavities to improve spectral purity and generate stable, narrowband beams. They are used in high-resolution spectroscopy and precision metrology.
Nd lasers are a subcategory of the solid-state laser family with neodymium-doped crystalline materials as the active medium. Neodymium lasers are constructed to emit a variety of spectra by varying the host crystal. Most Nd lasers produce 1.064 µm (IR). The introduction of a frequency doubler or a parametric oscillator can retune the beam to green, blue, and ultraviolet radiation. They deliver high-energy radiation with high efficiency, ideal for roles such as laser cutting, welding, and laser marking. Nd lasers can be operated in CW or pulsed mode. CW operation is suited to material processing, and pulsed Nd lasers are used in applications that require precise temporal control, such as laser-induced breakdown spectroscopy, range finding, and laser ablation.
Neodymium lasers are compact, long life, and robust, making them suitable for various applications: industrial integration, research laboratories, and portable applications. They are used in medical intervention in dermatology and ophthalmology, for procedures such as tattoo removal, skin resurfacing, hair removal, and treatment of vascular lesions. Neodymium lasers are often used as the pump source for other laser types.
Pulsed lasers are not of technology classification, but an operational mode. Any laser that is of a type that can emit in short, intense pulses rather than a continuous beam is adopted into this class. These lasers supply high-energy bursts of light with precise temporal control. Pulsed lasers fit a wide range of applications, including: research, materials processing, spectroscopy, imaging, medicine, and defense. Generating intense and precisely timed pulses of light facilitates various fields.
Pulses can be as short as a few femtoseconds, or much longer duration. This is dependent on the application needs, the excitation methods, and the laser technology. Short pulses allow complex uses in material analysis, spectroscopy, and atomic-level manipulation.
Choosing the exact laser type that best suits the needs of your application is not an easy task. The Venn diagram of operational capabilities is extensively overlapping, and the secondary factors like the price of equipment, price of ownership, and life expectancy add more complexity. Listed below are some of the factors to consider when choosing the type of laser:
- Application: A clear and realistic definition of the functional outcomes required will help to narrow the field of choice.
- Power Requirements: Understanding the application fully will allow a derivation of the power and service frequency required of the device. Powers can be thought of in bands, rather than exact levels. The cutting of 0.2 mm steel requires low tens of watts, whereas the cutting of 50 mm steel requires potentially 1000 times the power, for good throughput.
- Wavelength: A clear assessment of the application and power must be followed by the selection of an emission frequency that suits the application. Remaining with laser cutting as an example, precious metals require a different frequency from carbon composites. So, selecting a suitable spectral range is imperative for good function.
- Pulse Duration: Pulse length can vary from femtoseconds to continuous waves. However, establishing the ideal duration for your application can involve complex analysis. Tight control like laser engraving or skin treatment usually implies pulse mode, whereas steady-state operation requires continuous-wave (CW).
- Beam Quality: Your application may need extremely effective power that results from a small dot size and excellent Gaussian distribution, or it may have no need for this. Laser cutters work best when they have a small diameter and highly focused, quality beam. Data transmission in fiber optics is much more tolerant of beam quality, as the energy needed is less concentrated.
- Environmental Factors: Consider the environmental conditions in which the laser will be used. Factors such as temperature, humidity, and vibration can affect the performance and stability of the laser. Choose a laser that will tolerate expected conditions and operate reliably.
- Budget: Despite cost being a major factor for any equipment, this can only be considered once performance criteria have been applied as filters. The options field is wide for most applications, so budget choices still apply.
- Safety Considerations: Consider factors such as laser class, safety interlocks, and the need for personal protective equipment (PPE) in your application. Low-wattage lasers pose no hazards but should still be used with an eye to safety.
Laser cutting equipment uses CO2 lasers, as a rule. They are suited because of their low purchase cost, high power output, coherent/narrow beam quality, and effective absorption, particularly by organic materials. The high wattages available enable rapid and efficient cutting of the bulk of materials. The beam is absorbed by many metals, non-metals, and organic substances at 10.6 µm emission. High coherence and narrow beam diameter are suited to fine focusing and tight beam control, resulting in high effective power and clean cutting. Processing speed is optimal in many applications, allowing for high throughput.
CO2 laser cutting machines, on the other hand, can have difficulty initiating cutting with reflective metals, as the absorption spectrum of many such materials does not align with the 10.6 µm band. This can lead to the need for much higher initiation power. Once melting has commenced, the absorption property alters, and cutting can proceed.
Aside from CO2 lasers, fiber lasers, and Nd:YAG lasers are suited for special applications like precious metal cutting, in which their frequency is better absorbed by reflective, red spectrum (copper alloy) metals.
Yes, fiber lasers are extensively utilized for laser cutting applications, gaining market share in recent years as a consequence of excellent beam quality, high power efficiency, and small size. Fiber lasers are revolutionizing the laser cutting sector, enabling improved performance, energy efficiency, and versatility.
Laser engraving is commonly performed with a CO2 laser. This classification of laser offers a good balance between device cost, beam quality, power, and power modulation that renders them adapted to the delicate control required in laser engraving. Other laser classes, such as fiber and diode lasers can also be appropriate for specialist tasks, depending on the material and processing requirements.
Fiber lasers are becoming widespread in laser welding because of their particular characteristics such as: beam quality, power control, and robustness. These make them most amenable out of the available options. Fiber lasers offer improved performance, energy efficiency, and versatility. Their high radiant energy power, superior beam quality, and flexibility of control are advantageous in precise and efficient laser welding.
The majority of laser ablation machines are equipped with solid-state lasers, particularly the Nd:YAG subgroup. Their wavelength, power, beam performance, and durability suit ablation roles. While Nd:YAG lasers are extensively utilized in ablation tasks, other classes such as excimer lasers are suited to specific applications that require ultrashort pulses or particular wavelength requirements.
Fiber lasers show increasing popularity in plasma cutting. Their combination of high power capability, beneficial beam quality, advantageous processing speed, and flexible delivery (via optical fiber) are all advantages in this field.
High-energy lasers (HELs) and free electron lasers (FELs) are currently delivering the highest practical power levels available from the latest state of technology development. They can both deliver coherent radiation power levels in the megawatts (MW) to gigawatts (GW) range. In the more easily available, high volume, and lower price category, CO2 predominates in the high power range, with practical and system integrable devices commonly available in 100+ kW power at the point of application.
In industrial equipment for materials processing, CO2 is the most common type, combining good performance characteristics with low prices. In absolute numbers, the laser pointer and related devices are very widespread. They usually use either diode lasers or diode laser-pumped solid-state lasers. Diode lasers are also used in fiber-optic devices and most laser printers. They are increasingly used as initiator optical sources for larger and more complex devices. This makes diode lasers the most numerically common type of device.
Yes, a CO2 laser is a type of gas laser. CO2 lasers belong to the category of molecular gas lasers, in which the laser emission is generated by exciting the CO2 gas molecules to a higher energy state, discharging this energy through a number of other gas energy transitions to finally emit coherent photons.
This article presented the different types of lasers, explained each fo them, and discussed their various applications. To learn more about lasers, contact a Xometry representative.
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